1. Field of the Invention
The present invention relates to a color image processing apparatus and a color image forming method for forming a color image on a recording medium. The present invention is suitable for use in a color image output apparatus that forms an image by obtaining image data input from outside such as a color facsimile, a color printer, a color copier, etc., or a color printer software that operates inside a computer.
2. Description of the Related Art
In recording a full-color image with a color ink-jet printer, inks in three different colors, cyan C, magenta M, and yellow Y, or otherwise four colors, with the addition of black Bk to the above colors, are used to reproduce the colors of the original image. When the amount of discharged ink for each color approaches its maximum level, the amount of ink applied per unit area may be extremely large and the recording medium such as paper may not be able to soak up all the ink. Thus, the ink may spread out to other portions of the paper, or wrinkles may be created on the paper, thus significantly degrading the recording image quality.
In response to the above problem, various methods for controlling the total amount of ink and toner particles in a color ink-jet printer or a color laser printer have been proposed.
For example, in Japanese Patent Laid-Open Publication No.61-290060, an imaging method for recording an image is disclosed, wherein the total amount of recording material used in the recording is reduced when the total amount of a plurality of colors obtained for each pixel exceeds a predetermined value, while the input image data is processed so that the ratio of the cyan component to the magenta component to the yellow component will not be altered in the reproduced image. Also, in Japanese Patent Laid-Open Publication No.10-86413, a total ink quantity controlling method is disclosed, wherein multi-level image data are converted into bi-level data by reducing the multi-level data according to the size of the multi-level data of each color in the halftone image data.
As an example of an image output apparatus, an ink-jet printer represents an image tone (gray level) through a pseudo-halftone process using a plurality of dots of different sizes generated by changing the amount of discharged ink droplets according to an applied voltage and dither matrixes. FIG. 1A shows the relationship between the input gray level and dot size. FIGS. 1B, 1C, and 1D show the dither matrixes for the small dots, medium dots, and large dots, respectively. By way of example, when the input gray level is in the small dot range, the dither matrix of FIG. 1B for the small dots may be used to output small dots on the pixel positions corresponding to threshold values 2, 18, 6, 10, 14, 8, 24, 4, 20, 16, and 12 to reproduce the input gray level.
FIG. 2 shows the relationship between the recording control information and the actual amount of ink drops used in the above ink-jet printer. As is shown in FIG. 2, this relationship is nonlinear.
Basically, the above-described technology for controlling the total amount of coloring material has been developed for a case in which the relationship between the recording control information and the amount of ink drops is linear. Therefore, it is quite difficult to apply this technology to an ink-jet printer in which the relationship between the recording information and the ink drop level is nonlinear.
When a total amount of coloring materials is controlled using recording control information such as the CMYK multi-level data, the amount of ink applied per unit area will be different depending on the combination of the coloring materials; that is, the amount of ink varies depending on whether the relevant color is a primary color, a secondary color, or a tertiary color. For example, in a printer that establishes a relationship between the recording control information and the actual amount of ink drops used to be identical to that shown in FIG. 2, when the total amount of coloring materials is controlled so that the printer is prevented from recording with a total value of the recording control information for each color exceeding 150% of the maximum value for one single color, secondary colors such as blue (cyan: 255, magenta: 255) are recorded at approximately 7000 pl whereas tertiary colors (cyan: 255, magenta: 255, yellow: 255) are restricted to being recorded at around a total of 3000 pl. In such case, sufficient concentration cannot be obtained.
Further, when the relationship between the recording control information and the amount of ink drops is nonlinear, the ratio of colors will be altered even in reproducing secondary colors, that is, the suitable ink quantity can differ greatly even with just a difference in the hue. Thus, as a result of controlling the total amount of coloring materials, the color reproducing range that the printer is originally capable of recording may end up being minimized.
The present invention has been developed in response to the above mentioned problems of the related art and its general object is to make full use of the capabilities of a color image output apparatus upon reproducing the colors of the image.
Specifically, it is an object of the present invention to provide a color image processing apparatus that is capable of realizing color reproduction in a color image output apparatus having various features by controlling the total amount of coloring materials while making full use of the color reproducing range of the color image output apparatus.
Accordingly, a color image processing apparatus of the present invention for processing recording control information to reproduce a color image includes:
a converter that is adapted to convert the recording control information for each of color components into an amount of coloring material that is to be used after a halftone process; and
a total quantity control unit that is adapted to control the amount of coloring material of each color component based on a total amount of coloring materials of all the color components and a prescribed limit value.
Further, the recording control information may be arranged for an ink-jet printer, and the color image processing apparatus may include:
a first converter that is adapted to convert the recording control information for each of color components into an amount of ink drops that is to be used after a halftone process;
a total quantity control unit that is adapted to control the amount of ink drops of each color component based on a total amount of ink drops of all the color components and a prescribed ink drop limit value corresponding to an image forming condition; and
a second converter that is adapted to convert the controlled amount of ink drops into recording control information.
In this arrangement, the object of the present invention can be realized even in a case where the image forming condition is altered.
Additionally, the first converter and the second converter may perform a conversion by referring to a pre-established table providing a relationship between the recording control information and the amount of ink drops. This arrangement enables the object of the invention to be realized even when the relationship between the recording control information and the amount of ink drops in the image output apparatus is nonlinear.
Also, an image forming condition may include at least one of the material of a recording medium, the printing method, the resolution, the halftone processing method, or the color reproducing method. Thus, the object of the invention may be realized even when the image forming condition changes depending on for what purpose the color image device is used.
Further, the coloring materials may include a black coloring material, and the total quantity control unit is preferably adapted to control the amount of each coloring material other than the black coloring material. This arrangement prevents the degradation of black text contained in the image.
Additionally, the coloring materials may include cyan, magenta, and yellow, and the total quantity control unit is preferably adapted to control the amount of ink drops of each color component without changing the original ratio of the amount of coloring materials of cyan, magenta, and yellow. In this way, the object of the invention can be realized and the desired color can be reproduced.
It is another object of the present invention to provide a color image forming method that realizes color reproduction in a color image output apparatus having a variety of features by controlling the total amount of coloring material while making full use of the color reproducing range.
Such a color image forming method for reproducing a color image on a recording medium may include:
converting recording control information of each color component into an amount of coloring material that is to be used after a halftone process;
calculating a total amount of coloring material of all the color components; and
reducing the amount of coloring material of each color component when the total amount of coloring material exceeds a predetermined value.
It is a further object of the present invention to provide a storage medium storing a color image processing program that enables color reproduction in a color image output apparatus having a variety of features by controlling the total amount of coloring material while making full use of the color reproducing range.
Such a storage medium is adapted to store a program for processing recording control information to reproduce a color image in a color image output apparatus, the program containing instructions for a computer to perform procedures of:
converting recording control information of each color component into an amount of coloring material that is to be used after a halftone process;
calculating a total amount of coloring material of all the color components; and
reducing the amount of coloring material of each color component when the total amount of coloring material exceeds a predetermined value.